A liquid crystal display element has become used in watches, and electronic calculators, and also in various measurement instruments, automobile panels, word processors, electronic organizers, printers, computers, televisions, clocks, advertisement billboards, etc. The representative examples of the liquid crystal display method include a twisted nematic (TN) type, a super twisted nematic (STN) type, and a vertical alignment type using a thin film transistor (TFT), and an in-plane switching (IPS) type or a fringe field switching (FFS) type. The liquid crystal composition used in these liquid crystal display elements is required to be stable with respect to external impetuses such as water, air, heat, and light, and to exhibit a liquid crystal phase in a wider temperature range around room temperature as possible, and to have a low viscosity and a low driving voltage. Furthermore, the liquid crystal composition is constituted of several kinds of compounds to several dozens of compounds in order to make dielectric anisotropy (Δε) and refractive index anisotropy (Δn) optimal values in each display element. Furthermore, in all the driving methods including the vertical alignment (VA) type display as well as the horizontal alignment type display such as the TN type, the STN type, the IPS type or the FFS type, the liquid crystal composition which exhibits a low voltage driving, a high speed response, and a wide operating temperature range is required. In addition, it is necessary to adjust Δn of the liquid crystal composition to an appropriate range in accordance with the cell gap in order to set Δn×d which is the product of Δn and the cell gap (d) to a predetermined value. Additionally, in the case of applying the liquid crystal display element to a TV and the like, the liquid crystal composition is required to have a low rotational viscosity (γ1) since a high speed response property matters.
As a configuration of the p-type liquid crystal composition for such a high speed response property, for example, a liquid crystal composition including a compound represented by Formulas (A-1) and (A-2) which are liquid crystal compounds having a positive Δε and a liquid crystal compound (B) whose Δε is neutral in combination is disclosed. Characteristics of such a liquid crystal composition are that the liquid crystal compounds having positive Δε have a —CF2O— structure and the liquid crystal compounds having neutral Δε have an alkenyl group, and these are widely known in the field of liquid crystal compositions (PTL 1).

In addition, among factors that determine the image quality of the liquid crystal display used for liquid crystal televisions, smartphones, and the like, the stronger the three characteristics are exhibited, it is considered that the more the beauty increases in general, the three characteristics being the luminance which is the brightness of a screen, the contrast ratio which is the luminance ratio of white and black, and the gradation which controls the luminance of a pixel by the number of stages. Since the liquid crystal display is required to have visibility in a relatively bright place such as a living room, high level of luminance is required, and the larger the contrast is, the clearer the screen is. In addition, if the number of gradation increases, the number of colors that can be expressed also increases. For example, in general liquid crystal televisions, RGB pixels are controlled by 8 to 10 bits, respectively, and in the case of 8 bits, 16.78 million colors can be displayed in 256 gradations, and in the case of 10 bits, the number of colors that can be displayed in 1,024 gradations becomes about 1 billion colors. Accordingly, if the number of gradation simply increases, the image quality is also improved, but the shape of a transmittance-gradation voltage curve that divides the gradations also becomes an important factor.
That is, if the shape of a transmittance-gradation voltage curve is a slow curve such as linear shape, the divided gradation widths are equally spaced, and therefore the difference between the adjacent gradation voltages and the luminance displayed to correspond thereto becomes clear. However, if the vicinity of an inflection point of a transmittance-gradation voltage curve, or the curve is a curve shape of rapid change rate, the divided gradation widths are not equally spaced, and therefore the difference between the adjacent gradation voltages and the luminance displayed to correspond thereto is unlikely to occur. Due to this, the problem that the number of colors that can be displayed substantially decreases, occurs. Therefore, if there is a problem in expressive power of gradation, black defects in dark areas, halation in bright areas, or banding in intermediate gradation (vertical or horizontal streaks), color casts, and the like occur.
Examples of such a liquid crystal composition which makes the shape of a transmittance-gradation voltage curve flat include PTL 2. According to PTL 2, it is described that with a compound containing a —CH2CH2— linking group, a flat transmission characteristic curve is obtained.